Riccardia dimorpha sp. nov. (Hepaticophyta, Aneuraceae) from Western Nelson, New Zealand, exhibiting sexually-determined morphological dimorphism, an overlooked feature of some liverworts

Riccardia dimorpha is described from 24 collections made in New Zealand between1984 and 2020 from Western Nelson, Westland, and Fiordland ecological provincesin the South Island, and from Stewart Island / Rakiura. These specimens weremisidentified as R. browniae [ R. pusilla (Steph.) E .A.Br., n om. i lleg.], R . asperulataR.M.Schust., R. multicorpora E.A.Br., and R. perspicua E.A.Br., or identified only togenus. Riccardia dimorpha belongs to the Riccardia section Alcicornia Hässel and ischaracterised by having strong striations on the epidermis, a subterete thallus, amonopodial growth form, endomycorrhizae absent from the ventral epidermis, andepidermal cells are the same size as internal cells. Specimens were collected in fireinducedLeptospermum scoparium shrublands, on peat soils at lowland to montaneelevations. Riccardia dimorpha i s s exually d imorphic i n p lant s ize a nd n umber o fbranches (meristematic tip number), and male and female plants differ to the degreethat the sexuality of a plant can be determined without finding sexual branches on aplant. Such dimorphism is rarely reported in liverworts although is common in mosses.